In many applications such as scanned active imaging systems, optical radar, and the like, it is desirable to electronically change the direction of the laser output through a range of several degrees. Methods previously used to achieve the required deflection include mounting small mirrors on electrically driven tuning forks operating in a torsional mode. The deflected output beam from the laser always oscillates in the same direction. Another method includes electronically modulating the end reflectivity of a laser resonator. While both of these methods provide for output deflection scanning, both have inherent limitations and disadvantages.
With electrically driven tuning forks, deflection is limited in the variation of the driving frequency because of the required resonance with the mechanical frequency of the tuning fork. Also, this method does not provide random access to a predetermined direction. The latter method, on the other hand, while providing random access and a large range of scanning frequencies, requires large changes in reflectivity and high maximum reflectivity must be achieved.
It is an object of the present invention to provide a method which permits a high scanning frequency, random access and a relatively simple variation of scanning frequency. It is a further object of the present invention to provide a method for controlling the population inversion of a solid state laser to increase the output power subject to scanning.